Field of the Invention
This invention broadly relates to a process for preparing aliphatic alcohols from synthesis gas and more particularly to an improved process in which a sulfided heavy metal catalyst is employed to effect the hydrogenation of carbon monoxide to produce a mixture of lower aliphatic alcohols.
Lower aliphatic alcohols have been proposed as octane enhancers or as a replacement for gasoline in fueling internal combustion engines. Certain mixtures of lower aliphatic alcohols have the EPA approval for use and are currently being marketed in the United States. The lower aliphatic alcohols can be produced from domestically available non-petroleum sources and the use of these alcohols in fuel compositions can serve to lessen the nation's dependence on foreign sources of crude oil and petroleum products.
Hydrogen and carbon monoxide, or synthesis gas, a mixture of hydrogen and carbon monoxide, can be reacted to form a mixture of lower aliphatic alcohols. The synthesis gas feedstream can be produced from such non-petroleum sources as coal and biomass in well known partial oxidation reactions.
Numerous catalytic processes have been studied in attempts to provide a viable process for the production of aliphatic alcohols from synthesis gas. The early efforts were primarily directed to the production of methanol. More recently, attention has been directed to the production of higher aliphatic alcohols or a mixture of higher aliphatic alcohols with methanol. Such a mixture is highly suitable as an octane enhancing component for motor fuel and as a substitute for tetraalkyl lead additives in motor fuel.
A number of proposed processes have suggested the use of alkali promoted sulfided heavy metal catalysts for producing aliphatic alcohols from synthesis gas. These processes have an advantage in that sulfided heavy metal catalysts are more stable in the presence of minor amounts of sulfur compounds commonly found in the synthesis gas feed. However, the alcohol selectivity of sulfided heavy metal catalysts is adversely effected at higher reaction temperatures in the alcohol process.